1. Field of the Invention
The present invention relates to a vibration resistant bearing, its manufacturing method, and its application. The invention provides for a vibration resistant bearing, its manufacturing method, and its application, wherein a product having the bearing does not require extra packaging materials such as styrene foam and cushioning materials, or extra effort to arrange the products (orientation) for transportation on a badly conditioned road, and can be transported to a destination for its assembly without its performance deteriorating as a bearing.
2. Description of the Prior Art
In recent years, information devices, such as air conditioners, computers and VCR's, are manufactured in developing countries. However, a manufacturing location of parts such as motors is often a few hundreds to a few thousands kilometers away from an assembling location of the information devices such as air conditioners, computers, computer peripherals and VCR's. Therefore, when the parts are transported to an assembling factory, the race surfaces of bearings are often damaged due to vibrations on badly conditioned roads, and the performance of finely made bearings is often deteriorated.
Conventionally, bearings such as rolling ball bearings and roller bearings are used for information devices, and the ball or the race surfaces for rollers of the bearings are damaged by about 5 to 25 Hz of low frequency vibrations at the time of shipping in and out of transporting information devices. This phenomenon is called “fretting”. To solve this problem, an extreme-pressure additive has been added to a grease composition to fill in bearing spaces, as disclosed in Japanese unexamined patent application publication Nos. 2001-139979 and 2001-335792.
In a conventional method, an extreme-pressure additive is added only to the grease to fill bearing spaces and a rust-preventive film composed of the extreme-pressure additive is not formed on an inner and outer wheel and balls that compose the bearing. In this case, the extreme-pressure additive in the extreme-pressure additive grease does not fully coat rolling surfaces of each component, so the bearing will be damaged by fretting or the like, due to vibrations at the time of the transportation.
Conventionally, each bearing component such as an inner and outer wheel and a ball is cleaned to remove contamination. The cleaning processes are performed after the bearings have been mechanical processed, both before and after assembling, but before being filled with the grease. The contaminants often present are oil, debris, various organic substances and ion contaminants. Different cleaning liquids are used to clean each type of contaminant.
When the bearing components are made of ferrous materials, the cleaning processes causes those components to rust more easily because their surfaces have been activated. In addition, it should as well be noted that the oil on their surfaces is removed through the cleaning. Therefore, a process is required to prevent the bearings from rusting after the cleaning process. For this reason, there is usually a rust preventive process after the drying process in the cleaning process, where the bearing is immersed in a bath of a rust preventive processing solution that includes a volatile solvent and rust preventive oil. Here, a rust preventive agent is diluted to 1 to 5% by volume in the rust preventive oil. The rust preventive oil used in this rust preventive process is conventionally a rust preventive lubricating oil that mainly contains mineral oil, synthetic oil, etc. Here, the synthetic oil is carbonic ester, diester, polyol ester, poly(α-olefin) (PAO), etc.